JPH0556905B2 - - Google Patents

Abstract

A device for positioning/retaining a transducer relative to a body characterised in that it comprises a supporting member for placement on the body, connected thereto one end of a flexible and elongate arm, which has a mount for the transducer at or near the remote end thereof, and means for locking the arm in a fixed position relative to the body is disclosed. Also disclosed are an apparatus for monitoring aortic blood velocity and derived parameters by Dappler ultrasound and, optionally, ECG comprising such a device and that use of such an apparatus.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to extracorporeal cardiac output monitoring, and more particularly to an apparatus for such monitoring that is worn on a patient and used for extended periods of time or continuously.

BACKGROUND OF THE INVENTION Continuous monitoring of aortic blood flow velocity and guidance parameters using Doppler ultrasound or a combination of ECG and Doppler ultrasound has not been performed to date.

External monitoring of cardiac output refers to determining the amount of blood pressurized by the heart without inserting any instruments into the human body. The use of ultrasound devices has been proposed for this purpose, but this has major problems.

(Problems to be Solved by the Invention) In other words, since this device does not have a means to distinguish between desired blood flow caused by cardiac contraction and undesired blood flow caused by expansion, the measurement results are not reliable. It becomes something that does not exist. Furthermore, this device does not have a means for evaluating the signal-to-noise ratio of the blood flow signal, a necessary feature since a low signal-to-noise ratio will result in erroneous measurements. Additionally, the transducer must be accurately positioned and held under proper pressure to make meaningful measurements. For example, methods of positioning transducers using adhesive tapes have been only partially successful. Furthermore, especially for long-term use, the positioning means should not cause unnecessary pain to the patient and should allow movement of the body without interfering with the monitor. .

The present invention distinguishes blood flow due to cardiac contraction and cardiac expansion,
A device is provided that satisfies the requirements for evaluating signal-to-noise ratio and performing long-term transducer positioning, and provides significant benefits to the clinician.

Generally, cardiac output monitors based on ultrasound technology include a transducer having an ultrasound transmitting/receiving element that is manually secured to a notch in the patient's upper sternum. This converter is connected to the main measuring instrument by a cable. The instrument has a Doppler tip system that generates and transmits an ultrasound signal and receives the signal to provide a Doppler-shifted ultrasound acoustic output. This acoustic signal is sent to a spectrum analyzer or zero-crossing counter to extract the maximum frequency with high energy in real time. This maximum frequency represents the aortic blood flow velocity during systole, so integrating this function for each heartbeat gives the distance the blood moves with each heartbeat. This is generally called the stroke distance. Aortic cross-sections are obtained using direct measurements or nomograms. The product of stroke distance, aortic cross-sectional area, and heart rate is cardiac output, and this calculation is generally performed by software. The cardiac output thus obtained is displayed on an LED or LCD. In use, the transducer is placed in the upper sternal notch by hand and is used to measure certain scheduled values, such as the pitch of a sound from a loudspeaker, the displayed cardiac output value, or the peak frequency displayed on a bar graph. The target is operated until it reaches its maximum value. The cardiac output value thus obtained is recorded and the transducer is removed. Generally, such instruments have not been accepted by medical staff. One of the major problems is their low reliability, ie, the sensitivity of these measuring instruments to the interfering effects of other flows and movements of other tissues of the patient relative to the transducer. Errors may occur that the user is unaware of. Another major problem is that measurements are intermittent, such as in intracorporeal techniques that are being replaced by ultrasound. Continuous monitoring of cardiac output is highly desirable, for example, to enable monitoring throughout therapeutic procedures and testing.

(Means for Solving the Problems) The present invention includes a flexible and lockable arm, and a lockable arm provided near one end of the arm.
A human body for cardiac output detection having an ECG electrode, an ultrasound transducer provided near the other end of the arm, and a support member connected to the arm for fixedly attaching the ECG electrode to the human body. Provides a mounting device.

Generally, the arm consists of a plurality of interengaging segments that are screwed onto a single wire.
The wire is solid, but preferably braided, with minimal axial twist to vary the tension. These segments are fixed in position by tension means which may be in the form of a screw and lever or a cam and lever. These segments may all be made of the same material or of different materials, and may all be constructed with one end convex and the other concave, or may alternate between convex end segments and concave end segments. It may be placed in

The present invention also provides a device for monitoring aortic blood flow velocity and derived parameters using a combination of Doppler ultrasound and an ECG comprising a device of the present invention, and further provides a method of using such a device. It is something.

(Function) According to the present invention, a sensor device which is particularly suitable for external monitoring of cardiac output and is used by being attached to the human body is obtained. Generally, the device of the present invention is one that positions and holds a transducer, such as a conventional ultrasound transducer, tightly in a notch in the upper sternum. According to the invention, one transducer is attached to one end of the flexible fixable arm. This arm can be bent freely,
Moreover, it is possible to maintain a bent state. This transducer may then be connected to the Doppler tip within the meter. The arm consists of threaded segments, each segment preferably having a convex and a concave surface that aligns with the surface of an adjacent segment. These segments are made of glass fiber filled polycarbonate. Generally such segments are made elongated with suitable wire. At the end of this arm opposite the transducer there is a tensioning means which allows the segments to move relative to each other until tension is applied to the wire, providing a flexible arm allowing the desired positioning. Become. Once the transducer is in place, tension is applied to the wire to engage the segments and fix the shape of the arm. Tension can be applied in a variety of ways, but generally by adjusting screws, levers, and cams. This tensioning means is attached to the support member. For example, a three-legged plastic support member can be used, which can be secured onto the patient's chest so that the transducer can be positioned as desired. This support member can be secured to the chest in various ways. It may be secured with adhesive pads or with elastic straps or a combination thereof. A particularly suitable combination is the use of standard ECG electrodes by bonding with single-strand straps. This provides the necessary ECG signal to the main measuring instrument from the sensor that produces the Doppler signal.
Alternatively, the ECG signal may be obtained from a separate standard ECG lead.

(Embodiment) FIG. 1 shows a planar structure of an arm and a support member of an embodiment of the present invention. In this Figure 1,
Support member 11 supports tensioning means 12 . This tensioning device applies tension to a wire 13 in which the generally cylindrical spherical segments 14 and 15 that make up the arm are arranged alternately. A transducer 16 is mounted at the far end of this arm and is connected to a suitable monitoring device (not shown).

Corresponding reference numerals are also used in FIG. As can be seen from this embodiment, the support member 11 can be shaped to fit the patient's body and can hold the arms. Also as shown, the segment 15 has a spherical cross section.

FIG. 3 is a detail of the tensioning device of FIGS. 1 and 2. FIG. Basically, a pivot member (pivoting at 35) is provided such that the wire 13 passes through the member 31 closest to the arm containing the transducer and is fixed to the other member 32. Tension is applied or removed by opening or closing the pivot member. A threaded arrangement 33 is advantageous, which is adjusted by a knob 34.

In such cases, the device can be secured to the chest using two elastic straps, one on each arm, the ends of which are attached to the ends as support members.

In Figures 4 and 5, a support 41 or 51 supports a tensioning device 42 or 52. This tensioning device controls the tension in the wires 43 or 53, each having a partially spherical concave surface and supporting the segments constituting the arms. A transducer 44 or 54 is mounted at the far end of the arm and connects to a suitable monitoring device (not shown).

Furthermore, press stud sockets 45 or 55 are provided at the ends of each of the three legs of the support member in this embodiment.
is provided, and its dimensions are such that a standard ECG electrode press stud will fit therein.

ECG electrodes can be connected to or disconnected from the support member in this manner. Internal electrical connections are made to the press stud socket to obtain the ECG signal.

FIG. 6 is a detail of the tensioning device of FIGS. 4 and 5.
Basically, a stationary member 61 is provided, which has a rotating member 62 which is rotated by a lever 63. This rotary member is provided with an eccentric hole in the longitudinal direction, and this hole has a protrusion and the end of the wire 64 is fixed therein. This rotating member thus forms a cam,
When this drops, it gives tension.

We have found that by using a combination of Doppler ultrasound and ECG techniques, a more reliable measurement of aortic blood flow velocity and thus cardiac output is possible. The present invention provides a software algorithm using data from Doppler ultrasound and ECG that is particularly suitable for external monitoring of cardiac output.

The QRS complex of the ECG signal can be used as a time reference to distinguish between contractions and expansions. For example, contraction can be defined by the first half of the interbeat period and expansion by the second half. The desired aortic blood velocity signal from the Doppler sensor occurs without exception during this systolic phase. However, during the dilation period, the signal from the Doppler sensor is undesirable, such as non-aortic flow or movement or electrical noise. For each heartbeat, the characteristics of the Doppler signal, whether amplitude or frequency or both, are analyzed for contraction and expansion, respectively, using the ECG time reference. first,
Only Doppler signals obtained during systole are used for cardiac output calculations. The ratio of the parameters of this Doppler signal is then taken between contraction and expansion as a measure of signal quality and therefore reliability. For example, the maximum frequency of significant energy is integrated over systole and compared to the same time integrated over diastole.
If the ratio of these values does not reach a certain threshold, the beat is ignored as invalid or noise. Otherwise it is accepted as valid.

The ability of this measurement to distinguish between noisy beats and clear beats greatly increases its reliability.

The advantage of the contraction/expansion distinction is in the Doppler signal path.
This means that the AGC system can be activated only during systole. This improves the efficiency and speed of its response.

As another example, a basic modification of the measurement period using the present invention will be described below. FIG. 7 is a block diagram of such a measuring instrument. In the left part of this figure a probe or transducer connects to a conventional tip. There are means for recording and reproducing these signals. The Doppler signal and ECG signal are sampled at 25KHz and 100Hz, respectively, and these data are imported into the CPU via a double buffer memory system. This is where the spectral analysis takes place and all the algorithms and calculations needed to calculate cardiac output. Numerical results are sent to a 7-element LED for display, while graphical representations of the Doppler and ECG signals are sent to a CRT unit. You can get video output.

In use, standard ECG electrodes (referring to the preferred sensor shown) are plugged into connectors on each of the legs of the sensor. The sensor and electrodes are then placed on the chest, allowing the ultrasound transducer to enter a notch in the upper sternum. The neck strap is then placed behind the patient's neck so that each end connects to one of the upper two legs of the sensor.

Switch on this main measuring instrument and connect the sensor. Enter patient details on the keyboard to enable the meter to estimate the cross-sectional area of the aorta. The monitor is then started and an ECG trace is generated on the screen. A Doppler ultrasonic sensor is then placed.

Unlock the transducer by increasing the lock level, apply ultrasound gel to the transducer surface, and place the transducer in the upper sternum notch. The transducer then performs vertical and horizontal scans until the optimal systolic blood flow signal is received. The guidelines for this are the maximum peak contraction velocity and acceleration and the minimum amplification noise displayed on the CRT. Once the transducer is optimally positioned, the locking lever is depressed to secure the transducer in position and allow the monitor to be opened without a hand.

〔Effect of the invention〕

According to the present invention, the ECG electrode can be fixedly attached to the human body by the support member, and the ultrasound transducer can also be fixed to the human body at the same time by adjusting and locking the arm, so that ECG and Doppler ultrasound can be combined. Coordinated monitoring is possible and the patient is allowed some freedom of movement during this monitoring. By combining ECG and Doppler ultrasound, it is possible to monitor cardiac output while clearly distinguishing between the systolic and diastolic phases of the heart, making highly reliable measurements possible.

[Brief explanation of the drawing]

FIG. 1 is a plan view of the arm and support member of an embodiment of the present invention, FIG. 2 is a side view thereof, FIG. 3 is a detailed view of the tensioning device, and FIGS. 4, 5, and 6. is a similar diagram of one embodiment, and FIG. 7 is a block diagram of a measuring instrument employing the present invention. 11... Support member, 12... Tension device, 13...
...Wire, 14, 15...Segment, 16...
converter.

Claims (1)

[Claims] 1. A device that can be worn on a human body for detecting cardiac output of the human body, comprising: a flexible and lockable arm; and an ECG electrode provided near one end of the arm. an ultrasonic transducer provided near the other end of the arm; and a support member connected to the arm for fixedly attaching the ECG electrode to the human body. Body-worn device for. 2. The attachment device of claim 1, wherein said arm comprises a plurality of interengaging segments screwed onto a wire. 3. The mounting device of claim 2, further comprising a tensioning means wheel for increasing the tension in said wire to fix the relative position of said segments to lock said arm. 4. The mounting device of claim 3, wherein said tensioning means comprises a screw and lever arrangement or a cam and lever arrangement. 5. The segment according to claim 2, wherein each of the segments has a substantially convex surface and an opposing substantially concave surface, or the segments are arranged alternately with convex surfaces on both surfaces and concave surfaces on both surfaces. Mounting device. 6. A mounting device according to claim 1, wherein the support member is generally butterfly-shaped, triangular or tripod-shaped. 7. The mounting device according to any one of claims 1 to 6, wherein the support member has a means ring for holding it against the human body. 8. The mounting device of claim 7, wherein said retaining means is an adhesive ECG electrode and/or a strap.